Siemens SCALANCE M800 Operating Instructions Manual page 50

Connecting up
4.5 Digital input/output
Digital input
The 2-pin terminal block has the following assignment:
DI+
DI- (input ground)
If there is an adequate switching voltage at the digital input, the digital input is active and the
"DI" LED is lit.
50
24 VDC
-
Operating Instructions, 08/2018, C79000-G8976-C331-08
SCALANCE M874, M876